The present invention relates to full finctional testing of integrated circuit (IC) devices before assembly and particularly to a reusable device for making connections to singulated bare die.
There is an interest in performing full functional testing of unpackaged semiconductor die prior to packaging. This is due in part to the cost associated with packaging even singular IC devices. However, in addition to singular IC devices there is increased interest in full functional testing of individual IC devices before the individual devices are assembled into multi-chip modules (MCMs).
IC devices may be tested as follows. A semiconductor die is placed in a test chip package, e.g., a dual in-line package or a hermetic leaded chip carrier such as a flatpack, and die bonded by a temporary means. Thin wires are then connected from bond pads on the chip to leads in the chip package. The connections are typically made by wire bonding. The connections at the bond pads on the chip may be made in a way that results in a low strength bond. After the testing has been performed a force is applied to the wire to remove it from the bond pad on the chip, the die is then removed from the test package and subsequently packed in a production process.
U.S. patent application Ser. No. 08/591,365 entitled "Test and Tear Away Bond Pad Design" having a filing date of Jan. 25, 1996, and U.S. Patent Application entitled "Method for Providing a Test Connection and a Permanent Connection Site on an Unpackaged Semiconductor Die", filed Apr. 26, 1996 (Ser. No. 08/638,420), both of which as assigned to Honeywell Inc., are hereby incorporated by reference.
A known bare die testing method includes placing a bare die in a package or chip carrier and securing it there by temporary die bonding means, making temporary electrical connections from bond pads on the die to contact pads or leads on the carrier, and connecting external test equipment to leads on the carrier to perform electrical tests on the die. When the tests are completed, the die is removed from the carrier. Various means have been proposed for making the temporary die bond. For example, the use of a pre-cured RTV silicone strip commonly known as gel pack has been proposed for temporarily securing the die in place within a package body. The strip exhibits a surface static charge and coefficient of friction sufficient to hold the die in place without adhesive. A water soluble wax die bond has been used to secure the die to the package. Water soluble wax was found to be difficult to clean and the contamination also affected subsequent production wire bonding. An alternative technique utilizes a tape type die attach adhesive sold be E.I. DuPont deNemours of Wilmington, Del., under the trademark Kapton QA DuAttach Adhesive. The QL adhesive is heated, but for a shorter period of time than for permanently packaged die. The results in a lower strength which can be readily overcome when the testing is complete and the die is to be removed from the carrier.
In addition, it has been proposed to use a solution of sugar and water as a die attach adhesive. The technique would involve placing a drop of sugar and water on the package body or backside of the die and placing the die on the package. Surface tension would then retain the die in the package body until sufficient water evaporates to cause the die to be bonded to the package. Subsequent to testing, the package body would be placed in deionized water to free the die.
All of the methods for temporary die bonding just described are difficult to incorporate into a production process and include some contamination problems. All of these methods require some amount of clean-up which results in time inefficiency.
There is also a need for a test package that is reusable. The cost of test packages presently being used is significant if they are not reusable. The contamination problems associated with temporary die bonding methods make it more difficult to reuse the test packages.
Thus, a need exists for a simple and reliable method of providing temporary die bonding for testing purposes in a reusable package that is free of contamination problems.